We have recently upgraded from Solidworks 2012 SP. 5 and EPDM 12 to Solidworks 2013 SP. 3 and EPDM 13. Now we are getting this error when we try to check out files. Even if we close out of solidworks completely, the error still appears. We were on the phone with tech support and had a remote session in progress, and the tech said, "Oh I see you have Microsoft Outlooks opened, close that and try." This actually worked, which is really strange, but I don't want to have to close out of Outlook every time I want to check out a file. Now, it works if I open the file in Solidworks and try to check it out throught the EPDM add-in, but again, I don't want to have to open up the file just to check it out, for instance I may just want to update the data card.